Liquid crystal display device, which is a passive display device, comprises a backlight unit installed under a liquid crystal panel.
Backlight unit comprises a light source, an optical sheet, a frame, a bottom cover, etc. in a single module form and can provide light to a liquid crystal panel.
In the backlight unit, the light source receives a voltage from an external driving power source and emits light, however, can emit a heat incidentally. The heat emitted from the light source causes a thermal expansion of the optical sheet adjacent to the light source.
In consideration of the thermal expansion of the optical sheet, a frame surrounding an edge portion of the optical sheet can be spaced a predetermined distance apart from the optical sheet.